Ooh, how I wish I could buy put options on the Hyperloop. Because unless they solve the thermal expansion problem -- and there is no feasible solution on the horizon AFAICT -- they will fail.
This isn't true at all. The tube will still have air inside of it, you just need higher pressure behind the car than the air in front.
The cars themselves work a lot in the same way a cylindrical air hockey table would work.
The tensile stress at the ends of a hyperloop track would be orders of magnitude higher if you tried this approach. I haven't done the math, but I'd suspect you'd need an anchoring system comparable to what you see on large suspension bridge cables, if not more. Not only that, but I suspect you'd start to reach the limits of what steel can structurally sustain. With this solution, you've got a O(100km) long tube that is not only under vacuum but now also under enormous tension. Before this can be considered a viable solution someone needs to do the math on that, and AFAIK no one has.
So I still want my put options.
Because space has extremely low density thermal radiation doesn't really work very well... it's very hard for a vehicle in a vacuum to dump heat...there is no medium to receive the energy!
That's news to me. What do you think "cold" means if not a synonym for "low temperature"?
> Because space has extremely low density thermal radiation doesn't really work very well... it's very hard for a vehicle in a vacuum to dump heat...there is no medium to receive the energy!
No, that's completely wrong. It is very easy to radiate heat into space as long as your radiator is not pointed at the sun. What you can't do is convect heat away, which makes it hard to transfer heat from the hot part of a spacecraft to the cold part. But getting rid of the heat once you've transferred it to a radiator is really easy. In fact, some parts of a spacecraft need heaters to keep them warm if they don't get sun exposure.
People think high speed rail is expensive? Wait until you see how expensive Hyperloop is going to be per mile.
PS - And I haven't even touched on safety/evacuation problems with the concept. That quadupled the cost and size of the Eurotunnel for comparison, how can we assume it won't bloat the Hyperloop's size/cost/complexity?
You know what's expensive and was once unfeasible? Strapping thousands of tons of fuel to a rocket and launching it into space. And yet...
They're not trying anything at this point, they've raised enough money for at most 5km worth of high-speed tracks (proper 350km/h graded tracks) and no rolling stock.
Personally I don't think Musk is a "dummy" as you do, but I do feel sometimes his passion doesn't always address real world civil engineering limitations. The Hyperloop is technically very possible, thus isn't "dumb," it is just building it at scale (and addressing consumer safety, etc) that may be a challenge.
We build massive dams to stop rivers and invest billions into complex rockets that need to carefully control explosions in order to get people and cargo into space.
If one company can build a simple 10 ~ 20km tube between two major travel points in some country, it will be an invaluable proof of concept worth way more than the initial investment.
Just because something is hard doesn't me we shouldn't try.
For example, one mile of Hyperloop or five miles of conventional high speed rail? One mile of Hyperloop or two miles of Monorail? One mile of Hyperloop or investments into more efficient aircraft?
Remember, it's not enough to be smooth. You have to be:
1. Smooth (on the inside) and
2. Straight and
3. Strong (enough to bear the stress of having a multi-ton vehicle passing within a few millimeters at 700MPH) and
4. Long (300 miles at least) and
5. Airtight for that entire length, and
6. Cost-effective.
It is that combination of features that no one has ben able to even begin to tell a story about how they would make it work in the face of thermal expansion.
https://www.quora.com/Why-do-oil-pipelines-have-so-many-seem...
But this obviously won't work for the hyperloop. It has to be straight.
Space shuttles would have similar challenge (actually in reverse) - how to protect sealed air inside a closed cylinder from almost absolute vacuum outside in an environment where heat and cold are extreme; the cylinder being fabricated from overlapping conjoined pieces.
https://scholar.google.com/scholar?cluster=45818300884035476...
No alarms on thermal expansion, structural integrity etc.